This thesis investigates the Eighth Karmapa (1507-1554) and his Great Seal instructions. It demonstrates that the Eighth Karmapa was not only one of the most significant scholars of his school, but one who mastered and taught its highest meditational precepts. The thesis argues that analysing his Great Seal teachings through studying instruction-related genres in their historical, doctrinal, and literary contexts reveals a pedagogical pragmatism. It is more useful to view the Great Seal as an independent key instruction that the guru adapts to the students' needs, rather than a fixed doctrine. The thesis contributes significantly to the religious history of Tibet by interpreting a number of previously unstudied Tibetan sources. The main textual sources are selected spiritual biographies (rnam thar), question and answer texts (dris lari), meditation instructions (khrid), esoteric precepts (man ngag), and advices (slab byd) from the Collected Works of the Eighth Karmapa (2000-2004).